WLAN systems make use of the unlicensed bands for wireless communication. Transmissions of a wireless LAN (WLAN) communication system may be from a particular terminal to a desired destination, either another terminal within the same Basic Service System (BSS) or the backbone network, but always within the same carrier. There are two modes of operation for WLAN systems: ad-hoc and infrastructure. In the ad-hoc mode, terminals can talk to each other in a multipoint-to-multipoint fashion. In the infrastructure mode, an access point (AP) acts as a base station to control the transmissions among users, thus providing a point-to-multipoint wireless network. Since all the users share the same medium in a WLAN, the infrastructure mode becomes more efficient for semi-heavy to heavy loaded networks.
In an infrastructure mode, the terminal first communicates with the AP when sending data to a desired destination terminal. The AP in turn bridges or routes the information to the desired destination. Thus, in this mode, an AP of a WLAN communication system controls the transmissions within a BSS or cell.
Medium Access Control (MAC) protocols are defined to coordinate the channel usage for WLAN users sharing the band. These MAC protocols are based upon avoiding collisions between users as several users access the channel at the same time. The efficiency of a protocol is gauged by successful avoidance of collisions.
Two protocols used by WLAN are CSMA/CA MAC and CSMA/CD Ethernet protocol. Both protocols can sense the carrier for other transmissions. An Ethernet can be connected in various manners, including Ethernet hubs and Ethernet switches. An Ethernet hub concentrates the connections in a central point as a point-to-multipoint connection, with no impact on performance. An Ethernet switch operates every time that there is a packet arrival from a terminal. The switch reads the destination address, learns on which port it is connected and makes a direct connection between the two physical ports. The advantage of the Ethernet switch is that the MAC does not sense any other user in the medium, which improves performance through reduced probability of collisions and enhanced throughput as compared to an Ethernet hub. An Ethernet hub forwards a received packet to all users, even when there is only one intended receiver. The hub does not look at address information. The Ethernet switch only sends the packet directly to the intended destination, resulting in a more efficient usage of the available bandwidth.
A common WLAN AP is not capable of using more than one carrier frequency at the same time, which results in low protocol efficiency. Ethernet switches have proven to improve the efficiency of the Ethernet protocol considerably.
Therefore, what is needed is a method for improving the performance of a wireless point-to-multipoint network when the terminals share the same medium.